The United States Customary System was based on the British Imperial System. It is used in the United States and U.S. territories. In some parts it is similar to the Imperial units. Length or distance units include the inch, foot, yard and mile.
1 foot = 12 inches
1 yard = 3 feet = 36 inches
1 mile = 1,760 yards = 5,280 feet = 63,360 inches
As you can see from the above table, the U.S. system has no simple relation to each other, and the relations lack consistency. They are therefore difficult to remember.